The present invention relates to a semiconductor device production line and, more particularly, to a chemicomechanical polishing (CMP hereinafter) apparatus for polishing material layers formed an a semiconductor substrate.
Advances in the integration of semiconductor devices have led to the lamination of semiconductor substrates. Planarization technologies mainly directed toward interlayer insulating films are the key to the lamination of a semiconductor substrate. Among them, a planarization technology using a CMP apparatus is attracting increasing attention due to the progress of integration of semiconductor devices.
A conventional CMP apparatus includes a polishing platen and a polishing pad provided on the platen. While a slurry is fed to the polishing pad, a wafer is pressed against the pad. As a result, films formed on the wafer and including interlayer insulating films are polished.
However, the conventional CMP apparatus has some problems left unsolved, as follows. The slurry is dropped onto the center of the polishing pad and then spread away from the center simply by a centrifugal force. This prevents the slurry from being evenly fed to the interface between the wafer and the pad in a sufficient amount. As a result, each wafer cannot be evenly polished or cannot be polished at the same rate as the other wafers.
The polishing pad is formed of foam urethane or similar porous material having numerous projections and recesses on its surface. This, coupled with the fact that the slurry has some viscosity, prevents the slurry used to polish the wafer from being sufficiently removed by a centrifugal force available with the rotation of a conventional polishing platen. Consequently, the used slurry containing polishing waste remains on the polishing pad and scratches the next wafer.
The projections and recess of the polishing pad sequentially decrease due to repeated operation, resulting in a decrease in polishing rate. To preserve a desired polishing rate, it has been customary to condition the surface of the pad, i.e., to scan the pad with a conditioning disk while rotating the pad and feeding the slurry to the pad. The conditioning disk has diamond grains of 100 .mu.m.sup.2 buried therein. However, sore of the diamond chips come off the disk during conditioning and remain on the pad, scratching the surfaces of wafers to be polished.
Devices for polishing the surface of a semiconductor wafer are taught in, e.g., Japanese Patent Laid-Open Publication Nos. 5-13389 and 7-111256.